Proceedings of the 15th International Conference on Manufacturing Systems – ICMaSPublished by Editura Academiei Române, ISSN 1842-3183

“Politehnica” University of Bucharest, Machine and Manufacturing Systems DepartmentBucharest, Romania, 26 – 27 October, 2006

MACHINING IMPROVEMENTOF MILLING RAPID PROTOTYPING PROCESSES

Cristian COSMA, Adrian Ilie DUME, Eugen PAMINTAS, Tudor ICLANZAN

Abstract: A CNC tool can be used in many ways for prototyping, reverse engineering and modeling. Whitrapid prototyping tool, we can machine foam, wood, plastics, and aluminum to efficiently create proto-type and reproduction parts. This paper presents a technique for the manufacturing and finishing of partsby integrating RP and CNC machining.

Key words: rapid prototyping, milling, CNC, postprocessor, manufacturing.

1. INTRODUCTION

The term rapid prototyping (RP) refers to a class oftechnologies that can automatically construct physicalmodels from Computer-Aided Design (CAD) data.

Rapid prototyping techniques can be classified like inFig. 1.

The application of CNC milling as an RP technologystill is new, and has been made possible by a number ofnew developments. The use of CNC milling for prototypecreation is of course well known, however until recentlythis technique was not exactly Rapid. Main problem wasthe calculation of the toolpaths, for which a skilled CAMsoftware operator was needed.

This process involved the importing of several surfacepatches and the creation and checking of toolpaths forevery separate surface, which would take several hours.[2] A CNC tool can be used in many ways for prototyping,reverse engineering and modeling. Whit rapid prototypingtool, we can machine foam, wood, plastics, and aluminumto efficiently create prototype and reproduction parts.

With a CNC tool, we will typically be doing“subtractive” prototyping, but it is a process that lets youmachine quickly in materials that are similar to the endproduct. With a good CAD/CAM package and a CNCmachine, it is possible to create different parts.

Fig. 1. Rapid prototyping techniques [1].

The new software has solved the above problems,making CNC very suitable for Rapid Prototyping. Itsmain characteristics are:• import of IGES data instead;• no CAM-training needed: automatic toolpath genera-

tion;• low calculation times (fast);• low cost [3].

2. ELEMENTS OF RAPID PROTOTYPINGPROCESS THROUGH REMOVEDMATERIALS (MILLING)

2.1. Input

• material: natural woods, wood composites and hard,fibrous or abrasive plastics, aluminum.

• tool materials:– Solid Carbide: Use for all natural woods, wood com-

posites and hard, fibrous or abrasive plastics. Solidcarbide is generally the toughest tool (next to dia-mond tooling) and holds the edge best;

– High-Speed Steel: Use for aluminum, soft naturalwoods and ABS or poly plastics. High-speed steel isthe most readily available tooling and is preferred formost metal work because of its cost and hardness. HSSis seldom used in wood applications because carbidetooling stays sharper longer. HSS is generally preferredfor metal cutting and some plastic cutting operations.

• fixturing & tool changing systems: the surfaces oftables are usually slotted to allow for the mechanicalfixturing of workpieces. The T-slots on the tableaccept T-nuts which the operator can use to secureclamps and bars. For tool changing we use a systempresented in the Fig. 2.Even if the tool is not inserted to a consistent length,

the tool tip is located precisely by the sensor.• cutting parameters: these parameters are done by

the soft. This type of software allows the user to inputparameters such as cutter size, finish quality, andnumber of passes over the material. Based on thespecified parameters, the CAM program then calcu-lates the toolpath.

• part complexity: we can manufacturing 2-D and 3-Dcontours, pockets with island avoidance, surface of

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Fig. 2. Tool Touch-Off Sensor.

revolution, arbitrary 3-D surfaces, intersecting sur-faces, inlays, etc.

2.2. Output

• quality of surface• time of manufacturing• rest of uncut material• dynamic behavior in the manufacturing process

3. EQUIPMENT AND SOFT

3.1. Rapid prototyping machine

The isel-CNC base units of the series GFM 4433 arestable C-frame-type CNC machines made of light-weightprofiles (Fig. 3). All linear axes run on grinded steelshafts with linear ball bearings. Clearance-free ball screwdrives with hardened and polished 5/8''-16 spindles witha pitch of, optionally, 5 or 10 mm are used as drives. Thelinear axes are driven by powerful and robust steppingmotors (series GFS) and DC servo motors (series GFV)in easy-to-maintain drive modules.

The machine table, which is firmly screwed with theunderframe, is made of plan-milled precision T-nut pro-files. It provides optimal clamping possibilities for themost different and workpiece holders and devises. Theprotective hood, which features Perspex-lined glass and a

Fig. 3. The ISEL rapid prototyping machine.

swivelling door made of aluminum profiles, constitutes aclosed working room with hood locking. The isel-CNCbase units of the series GFS 4433 are ideal for individuallyassembling applications in the fields: positioning, milling/drilling, graving, dosing, screwing, measuring, etc.

3.2. Soft

We will use Edge Cam soft. Edge CAM offers a fullrange of surface machining functionality that can be usedby the production machinist equally effectively to machinelarge quantity batches.

Intelligent approach strategies provide improvedsurface finish while optimizing machining times andmaximizing tool life. With Edge CAM, everything isverified on screen before it goes to the machine. Theoperators can even check the level of surface finish thatmight be achieved. The numeric code is generated usingAutomatic Programming Tooling (APT).

3.3. Postprocessor for rapid prototyping machine

The rapid prototyping machine was getter from ISELfirm. In the moment of getter, it came accompaniment bya drawing soft that is on DOS; allow only drawing and2D importation drawings.

Also, the CAM soft presented a disaffected commu-nication interface, being deficient in menu. The fabrica-tion was one of counter. Knowing that the machine is2.5D, I wished to can realize 3D models importation.That was not possible, on display coming on each timemessages who advertise me that this operation it is notpossible. So I go on to write back the postprocessor ofprototyping machine, refreshing his functions [4]. Currentcomputer-aided manufacturing CAM software is readilycapable of generating toolpaths given a set of surfaces ofa part and a cutting orientation 3-axis machining [5].

The steps for postprocessor writhing are:• Definition of machine: for this we will use Code

Wizard module from Edge Cam soft (Fig. 4).• Instructions writing: we will choose a postprocessor

who will be adapted for our machine. We set up allthe instruction. This is presented in Fig. 5.

Fig. 4. Start of postprocessor writing.

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Fig. 5. Instructions writing.

4. TECHNIQUE FOR THE MANUFACTURING

This paper presents a technique for the manufacturingand finishing of parts by integrating RP and CNCmachining. When using CNC machining to finish theparts, pre-processing of the original 3D model andquickly and correctly generating tool paths and machinecode from the 3D model are very important issues.

The accuracy and surface finish of parts manufac-tured by RP are material and process dependent. Consid-ering both accuracy and machining efficiency, themachining strategy of adaptive raster milling of the sur-face, plus sharp edge contour machining, is applied tofinish the RP parts and tools. For finish machining ofrapid manufactured parts or tools, the degree of automa-tion and the total time used to generate tool paths fromthe model are important criteria. It is more important togenerate tool paths automatically and quickly than togenerate high efficiency machine code. This study showsan initial applicability of the presented procedure and theimproved capabilities of this machining strategy forfinish machining of rapid manufactured parts.

To present the methodology of rapid prototyping wewill use a car model. We begin whit the interior part.

Steps for manufactured parts in rapid prototypingprocess through removed material (milling):

First we will choose stock and CPL (Fig. 6).

Fig. 6. Stock and CPL choosing.

Than we will initiation the first sequence and we willchoose the right tool milling for Z Level Roughing Cycle(Fig. 7).

The next step is to establish the strategy of roughness,mill type, cutting parameters, etc. (Fig. 8).

Like the steps above, we will make the same thingbut for finishing cycle (Fig. 9).

EdgeCAM Simulator provides full 4-axis representa-tion, providing sequence verification before the machin-ing process commences. In this way the probability tomake a fault is minimal.

Fig. 7. Choosing tool milling.

Fig. 8. Z Level Roughing Cycle.

Fig. 9. Z Level Finishing Cycle.

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In figure below is presented the part after the simula-tion of the virtual manufacturing (Fig. 10).

The exterior part after the simulation of the virtualmanufacturing is presented in figure below (Fig. 11).

The last step is to generate numeric command:N000001 IMF_PBLN000002 FASTVEL 10000N000003 FASTABS X0 Y0N000004 FASTABS Z10N000005 ;(USER DEFINED)N000006 COOLANT ONN000007 FASTABS X12622 Y86771N000008 FASTABS Z61341N000009 FASTABS X12622 Y86771 Z5000N000010 MOVEABS X12622 Y86771 Z-2000……………………………………………………N000115 MOVEABS X9965 Y54866 Z-2000N000116 CCWABS I12960 J55207 X10115 Y54212Z-2000N000117 MOVEABS X10209 Y53965 Z-2000……………………………………………………N061661 MOVEABS X20730 Y3357 Z-27400N061662 CCWABS I20147 J-1609 X15288 Y-433Z-27400N061663 MOVEABS X15181 Y-1027 Z-27400N061664 MOVEABS X25092 Y-2208 Z-27400

Fig. 10. Part in simulation mode.

Fig. 11. Exterior part in simulation mode.

Fig. 12. Some examples of different parts.

N061665 MOVEABS X25092 Y-2208 Z-27600N061666 CCWABS I20128 J-1607 X20730 Y3357Z-27600N061667 MOVEABS X18688 Y3604 Z-27600.

5. CONCLUSION

This paper presented a methodology for rapid prototypingin CNC milling. The method makes it possible to rapidlycreate machined parts and prototypes with little orno human intervention. The method can be used formoderately complex part geometries.

We have shown that CNC milling is a competingtechnology for Rapid Prototyping. Some examples ofdifferent parts make in rapid prototyping process throughremoved material is present in Fig. 12.

REFERENCES

[1] Onuh, S.O., Yusuf, Y. Y. (1999). Journal of IntelligentManufacturing, 10, pp. 301–311, Kluwer AcademicPublishers.

[2] *** (1998). The DeskProto approach offers true Concept Mod-elling, Prototyping Technology International, pp. 110–114,http://www.deskproto.com/download/articleprottechint98.htm.

[3] Nikam, Pratik E. (2005). Application of subtractiverapidprototyping to the design and manufacture ofrapid solidification process tooling, Spring, http://www.forging.org/FIERF/pdf/SRP_CSUFinalReport.pdf.

[4] Cosma, Cristian, Adrian-Ilie, Dume, Iclanzan, Tudor (2006).Virtual Design and Automation, Manufacturing Methodologyfor the Milling Rapid Prototyping Process, ISBN 83-7143-228-3, Poznan.

[5] Ye, Li., Matthew C., Frank (2006). Machinability Analysisfor 3-Axis Flat End Milling, pp. 454–464, Journal of Manu-facturing Science and Engineering, vol. 128, http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=JMSEFK000128000002000454000001&idtype=cvips&prog=normal

Authors:Cristian COSMA, Ph.D. Student, “Politehnica” University ofTimişoara, Manufacturing and Material Engineering,E-mail: ccosma@eng.upt.roAdrian Ilie DUME, Ph.D. Student, “Politehnica” University ofTimişoara, Manufacturing and Material Engineering,E-mail: adume@eng.upt.roEugen PAMINTAS, Assoc. Prof., “Politehnica” University ofTimişoara, Manufacturing and Material Engineering,E-mail: epamintas@eng.upt.roTudor ICLANZAN, Prof., “Politehnica” University ofTimişoara, Manufacturing and Material Engineering,E-mail: ticlanzan@eng.upt.ro